My son received a 1099 Misc form this year. His employer provides the truck and a gas allowance. I don't know which form we need to complete for the IRA.

Assuming you are talking about IRS instead of IRA, he should fill out the form 1040 (schedule C), Profit and Loss for Business, along with his regular 1040. All these forms can be downloaded from the IRS website.

Schedule E allows you to report the income, stated in the 1099 MISC, and the expenses you incurred in order to get that income, as deduction to reach the net amount in Schedule C. This amount will become one line item on your 1040. Read through the insturction with the tax forms then you will know how to fill them out. It will take about 1 hour for the schedule C if this is your first time.

If your son is your dependent, then it became the question of how much he made this year to determine whether he should file his own return or not. That's another question.